.Here is a spiel on Victorian rainforests from the 1994 Native Forest Network Australian Forest Conference.
PRESSURES ON VICTORIAN RAINFORESTS
Victoria's foremost forest expert on rainforests, David Cameron should be giving this address. However, he has been denied permission to speak by his employers, the Department of Conservation and Natural Resources. There is no positive purpose served by not allowing him to speak.
Victoria's rainforests are found in small pockets in East Gippsland, the Central Highlands, the Otways and Strzelecki Ranges. They occur principally along small streams and creek lines in the areas protected from the major determinant of rainforest distribution, fire. These areas are usually well shaded and moist, and generally have a high rainfall. A conservative estimate of mature, eucalypt - free rainforest in Victoria is about 15,800 hectares. The true figure for Victorian rainforest is probably somewhere closer to 25,000-40,000 ha when mixed forest and other secondary types are included, as well as minor occurences. These rainforests often occur in small, isolated stands in a lineal or branch shape, giving it a high circumference to area ratio and exposing it to greater potential impact from disturbance and surrounding forest.
College Ck., Strezlecki Ranges
There are three distinct rainforest types in Victoria; cool -temperate, warm-temperate and dry rainforest. Cool-temperate rainforest is found in areas of high to very high rainfall and from sea level to sub-alpine elevations. Major occurences are in the Otways and Strzelecki Ranges, Central Highlands and Errinundra Plateau in East Gippsland. It's usually dominated by Myrtle beech and or/Sassafras. Mist and fog are common at high elevations and this rainforest type is often located along creeklines and sheltered mountains, slopes and gently undulating mountain plateaus.
Warm-temperate rainforest is found in areas of moderate to high rainfall and elevations from sea level to 800 metres. It's often found in sheltered gullies and gully heads and along humid lowland river valleys. Its' major occurences are at Wilson's Promontory and the coastal plains and foothills of East Gippsland. The dominant canopy tree is usually Lilly Pilly with Blackwood a common emergent.
Dry rainforest is found in areas of low to moderate rainfall and low land foothill elevations. It's located in distinctly fire-proof niches, including dry rocky gorges and rocky outcrops and along warm, inland rain-shadowed valleys. The only dominant canopy tree is Sweet Pittosporum. This type is located in East Gippsland along the Mitchell, Snowy and Murrundal Rivers.
The distribution of rainforest in Victoria is controlled by fire, given minimum water requirements are satisfied and extremes of temperature are not limiting. The existence of dry rainforest with only a minimum of 600 millimetres of rainfall required illustrates that rainfall need not be the major determinant of rainforest distribution as is often assumed. Rainforest has existed in a dynamic and ever changing relationship with Schlerophyll or Eucalypt forest for millions of years. As climatic conditions have changed over this time, the distribution of the fire-sensitive rainforest has changed and the fire-adapted eucalypt forest has responded accordingly. As the Australian continent has become drier and warmer, promoting conditions more condusive to fire, the extent of Schlerophyll forest has expanded, while the distribution of rainforest has contracted to small, and relatively fire-free niches. The situation continues today, with small rainforest refuges surrounded by a sea of ecologically antagonistic Schlerophyll vegetation. Vegetation that in contrast to rainforest is well adapted to fire.
Mixed forest is defined as a rainforest understorey with a eucalypt overstorey and represents a stage in post fire succession which may lead, in the absence of further fire, to the establishment of a mature or primary, eucalypt free rainforest. Mixed forest is essentially rainforest with eucalypt emergents through a rainforest canopy. The presence of a eucalypt overstorey indictates a history of disturbance within the rainforest. To understand how rainforests have survived in Victoria, it's important to understand the basic ecological processes which allow rainforest to survive when often surrounded by highly flammable and fire-adapted eucalypt species, and other species in this, one of the world's most fire prone regions. Rainforests have survived in Victoria because there have been refuges when it could retreat to when the environment became hostile. These have protected rainforest stands from the potentially devastating effects of fire, and include locations in deep valleys and creek lines, generally damp and moist environments where fire is less likely to penetrate.
In these catchments there is typically a progression of vegetation types; beginning higher up with dry and damp forest types, moving down from damp into wet forest, and riparian forests and eventually into rainforest in the lowest elevation or most protected part of the catchment. The dry and damp forests are usually located on or near ridges and upper slopes. They, especially the dry forests, receive the most light, heat and drying winds. Consequently, fire is frequent and intense in these forests, and species are usually resistant and well adapted to it. Here, fire burns with a higher intensity and will pose a threat to rainforest were it not for the taller and wetter forests down the slope. Protected from the extremes of sunlight, heat and wind, these downslope forests remain moist during most summers and because of this, fire is a rare occurrence. The higher moisture status of wetter forest types is critical in limiting the spread of fire down slope into rainforest, and also in limiting the down slope expansion of more flammable and combustible up-slope communities. In addition, where rainforest and eucalypt forest meet, the taller and moister surrounding forest acts as a buffer to fire, reducing its spread into the rainforest. The height of mature or old growth wet forest eucalypt species, compared to that of rainforest trees, means that approaching fire will often jump the rainforest patch, rather than incinerating it. The taller eucalypts act to shield the rainforest area from fire by absorbing radiant heat as well as reducing the impact of dry winds and storms entering the rainforest. These old growth eucalypt forests are essentially an ecological buffer for the rainforest. It can be seen then that a more natural fire regime associated with old growth forest is critical to rainforest survival, as is the management of those catchments.
A lot has been said about the fire management practices of the Australian Aboriginal people prior to European settlement, and the fire regimes they imposed on the Australian landscape. While there is little doubt that they used fire for many purposes, little is documented about burning practices in Victoria. Recent studies suggest that European settlement has had significant impact on fire regimes in upland and wetter forest areas of Victoria. Extensive and more intensive fires have become more frequent, affecting the ecological processes operating in catchments surrounding rainforest, having obvious implications for its survival.
Activities within catchments containing rainforest and which alter the fire regimes within those catchments, can directly threaten the survival of those rainforest stands. An increase in the frequency or intensity of fire may lead in the medium to longer term, to the eventual elimination of those rainforest stands. This is because most rainforest species are fire sensitive, easily killed by intense fire, and may therefore be eliminated from the site. Such species can only return to a burnt area from unburnt refuges once conditions have become suitable again. Other rainforest species, including some larger trees, are killed by intense fire but may resprout from the root system after mild fire.
Disturbance can have a destabilising effect on the ecological processes which maintain the balance of an essentially stable ecosystem. How disturbance effects these ecosystems is a complex subject, and one which has not received the investigation it deserves. It is possible to identify the key issues in three points:
1. Increased human activity in these catchments and sub-catchments containing rainforest, increases the likelihood of fire. About 60% of all public land fires can be attributed to human origin. The most common cause of fire of human origin are those relating to escapes, relights and burining off, and fuel reduction burns; in other words, forest management techniques. Arson is also a major cause of fire. So when forest roads and logging tracks are put into bush, the chances of fire starting are greatly increased.
2. An increase in fire frequency promotes selective regeneration of more flammable, fire tolerant, and fire promoting species. Simply put, more frequent fires favour those species which are adapted to more frequent fires and don't favour those species which are not well adapted to fire. This process has been noted in many parts of Victoria, including the early Forest Commission reports. Silvertop, for example does particularly well at outcompeting less fire-adapted species. The result of this process is to encourage the downhill expansion of more fire-adapted upslope species. Having previously spoken of how stable catchment processes protect rainforest, this clearly raises the risk of intense fire occurring close to the rainforest stand.
3. There is a significant and growing body of evidence to suggest that timber harvesting is encouraging the regeneration of more fire-adapted species. This again, has been noted in early Forest Commission reports and confirms that species such as Silvertop, which responds so well to regular fires, also responds prolifically after harvesting. It's now established that clearfell harvesting promotes regeneration of more light-adapted and fire promoting species. Recent studies support the proposition that there is a downslope expansion of species more typical of drier forest types after harvesting, thus increasing the likelihood of intense fire threatening the rainforest stand. In addition, the logging of tall eucalypts within the ecological buffer surrounding rainforest stands threatens the survival of those rainforest stands. While rainforest ecological buffers may be of varying width, prescriptive buffers in areas subject to timber harvesting, are just twenty to forty metres wide. These prescriptive buffer widths are arbitrarily defined and don't take account of ecological realities. Their value can at best, be described as unproven and limited, and at worst, utterly inadequate.